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How to wire a 7 Pin (12 S type) Caravan Plug

There are some important differences in the 12S socket wiring in caravans manufactured prior to 1999 and after 1999. The 12S cable sizes for post 1999 models have been increased to reduce voltage drop and improve load capacity. The car charge line (blue cable) is now left unused, the caravan battery is now charged via the green cable whilst the car engine is running, when the car is not running the green cable reverts to providing a power supply from the car battery, this action is produced from a relay fitted in the caravan. Also the fridge negative has been separated to reduce the loading on the system which unfortunately may cause compatibility issues with some older cars.

12S Wiring Diagram, PRE 1999 (BRITISH STANDARDS)

Pin No.

Cable colour

Function

1

Yellow

Reversing light

2

Blue

Ignition positive (for battery charging)

3

White

Common Return

4

Green

Power feed for internal 12v equipment (not fridge)

5

Brown

Spare

6

Red

Refrigerator (via relay in car)

7

Black

Spare

12S Wiring Diagram, POST 1999 (EUROPEAN STANDARDS)

Pin No.

Cable colour

Function

1

Yellow

Reversing light

2

Blue

Spare

3

White

Return for circuits connected to Pin 4

4

Green

Power feed for internal 12v equipment or to charge caravan battery via a relay in the caravan (not fridge)

5

Brown

Spare

6

Red

Refrigerator (via relay in car)

7

Black

Return for circuit connected to Pin 6

Please Note: That when wiring the 12S socket, independantly wire Pins 3 & 7 to the car. This increases the wire load capacity and prevents overheating.